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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4><a name = "tag_000_007_1768">&nbsp;</a>NAME</h4><blockquote>
putenv - change or add a value to environment
</blockquote><h4><a name = "tag_000_007_1769">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;<a href="stdlib.h.html">stdlib.h</a>&gt;

int putenv(char *<i>string</i>);
</code>
</pre>
</blockquote><h4><a name = "tag_000_007_1770">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>putenv()</i>
function uses the
<i>string</i>
argument to set environment variable values.  The
<i>string</i>
argument should point to a string of the form "<i>name</i>=<i>value</i>".
The
<i>putenv()</i>
function makes the value of the environment variable
<i>name</i>
equal to
<i>value</i>
by altering an existing variable or creating a new one.
In either case, the string pointed to by
<i>string</i>
becomes part of the
environment, so altering the string will change the environment.
The space used by
<i>string</i>
is no longer used once a new string-defining
<i>name</i>
is passed to
<i>putenv()</i>.
<p>
This interface need not be reentrant.
</blockquote><h4><a name = "tag_000_007_1771">&nbsp;</a>RETURN VALUE</h4><blockquote>
Upon successful completion,
<i>putenv()</i>
returns 0.  Otherwise, it returns a non-zero value and sets
<i>errno</i>
to indicate the error.
</blockquote><h4><a name = "tag_000_007_1772">&nbsp;</a>ERRORS</h4><blockquote>
The
<i>putenv()</i>
function may fail if:
<dl compact>

<dt>[ENOMEM]<dd>
Insufficient memory was available.

</dl>
</blockquote><h4><a name = "tag_000_007_1773">&nbsp;</a>EXAMPLES</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_1774">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
The
<i>putenv()</i>
function manipulates the environment pointed to by
<i>environ</i>,
and can be used in conjunction with
<i><a href="getenv.html">getenv()</a></i>.
<p>
This routine may use
<i><a href="malloc.html">malloc()</a></i>
to enlarge the environment.
<p>
A potential error is to call
<i>putenv()</i>
with an automatic variable as the argument, then return from the calling
function while
<i>string</i>
is still part of the environment.
</blockquote><h4><a name = "tag_000_007_1775">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_007_1776">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="exec.html">exec</a></i>,
<i><a href="getenv.html">getenv()</a></i>,
<i><a href="malloc.html">malloc()</a></i>,
<i><a href="stdlib.h.html">&lt;stdlib.h&gt;</a></i>.
</blockquote><h4>DERIVATION</h4><blockquote>
Derived from Issue 1 of the SVID.
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UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
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